In many industries, large quantities of compressible materials must be stored and transported around. Compressing these materials into smaller volumes often results in significant cost savings. Fibreglass thermal/acoustical insulation (glass wool), mineral wool products (rock wool, slag wool), fabrics or mats of organic or inorganic materials, and compressible foam materials such as polyurethane foam blankets are just a few examples of materials which are more efficiently handled in a compressed form.
The need for substantially reducing the volume of light density thermal/acoustical fibreglass insulation products for shipping and storing is clear. Common fibreglass insulation products such as types R-11, R-13 and R-19, have densities ranging from 0.52 to 0.60-pcf (pounds per cubic foot). Because the density of the glasses used to make this insulation lies roughly in the range of 2,600 to 2,800 kg/m3, it can be determined that the actual volume occupied by the glass is often less than 0.5% of the total product volume. Handling such a bulky product without any compression is clearly impractical, particularly from an economic point of view. It is therefore common practice to substantially reduce the product volume by roll winding and other packaging processes. However, compression cannot be allowed to damage the product to the point that it does not recover its nominal thickness and performance levels after unpacking. Lack of thickness and performance recovery directly translate into some loss in product utility and value, defeating the purpose of the exercise.
Compression of fibreglass products is typically performed in either a one-stage process or a two-stage process. The leading one-stage technique is winding of the compressible material into a compressed roll. In some processes a second stage is performed to compress the already rolled material, either by applying direct mechanical force or a vacuum. During the final stage of bundling rolls together, typically in units of four, some additional pressure may also be exerted, for example, using a stretch wrap.
Over the years a large variety of roll-up machine designs have been developed, but in principle, they can be grouped into just a few general categories. Of particular interest are the following:    1. mandrel-based designs;    2. single-belt, “free-loop” designs;    3. triangular cavity designs;    4. rigid arcuate jaw designs; and    5. circular cavity designs.
An exemplary mandrel-based design is presented in FIG. 1. Mandrel-based designs employ a mandrel 110 against which the leading edge of the insulation blanket 112 is held for rolling-up. The mandrel 110 is then rotated and the compressible material rolled up on the mandrel 110, meanwhile being compressed using some system of continuous belts (in this case, first by continuous belt 114, and then by belt 116). In the case of FIG. 1, the position of rollers 118 and 120 are adjusted as the roll grows, as are rollers 122 and 124.
These machines typically overcompress the leading portion of the blanket, causing some loss in thermal insulation value for this portion due to lack of product thickness recovery after unpacking. U.S. Pat. No. 5,832,696 discloses an exemplary version of such a mandrel-type roll-up machine.
A mandrel-type roll-up machine with automatic, rather than manual, tucking and starting of the compressible sheet material on a mandrel is disclosed in U.S. Pat. No. 6,286,419. While this design operates more quickly and efficiently than that of the '696 patent, it still suffers from the deficiency of over-compressing the leading edge of the material being rolled. Typically, roll-up machines of this type are used for rolling relatively thin compressible sheet material ranging in thickness from 0.5 inch to 2 inches. It is desirable that roll-up machines be able to handle much thicker materials, for example, in the range of about 1.5-inches up to 9-inches.
Another class of roll-up machines uses a continuous, single-belt loop in a “free-loop” configuration. An exemplary “free-loop” design is shown in FIG. 2. The compressible material 112 is transported by a belt conveyor, and enters a cavity or loop 132 formed by a single continuous belt 134. The single continuous belt 134 is held at the entry point for the compressible material by a combination of a fixed roller 136 and a series of rollers 138 or a properly shaped belt conveyor, which also serves to support the rolled product weight. This is referred to as a “free-loop” design because there are no guides which cause the free-loop to take on any particular shape; hence, the roll will take on a generally circular or oval cross-section.
Over the years, numerous improvements were made to this single-belt concept, details of which can be found in the following U.S. Pat. Nos. 3,133,386; 3,911,641; 3,964,235; 4,114,530; 4,163,353; 4,164,177; 4,602,471; 4,653,397; 4,896,476 and 6,321,507. While roll-up machines of the single-belt “free-loop” design offer some advantages over mandrel-based designs, they still suffer from several major operational deficiencies.
As explained in U.S. Pat. No. 6,321,507, the conventional, single-belt “free-loop” design, with a fixed belt width, has a limited ability to efficiently package compressible materials of various widths. Attempts to operate this roll-up machine with less than a full belt width of compressible material results in what is referred to as “telescoping” or “coning”, that is, a relative axial shift or displacement of subsequent concentric layers of the rolled strips of material with respect to each other. Telescoping complicates the wrapping of the roll product with a sheet material (such as a plastic film) as overall, the roll is now longer than it should be. As well, the ends of the roll are conical instead of flat, making stacking in a warehouse or storage facility difficult.
To avoid telescoping during the roll forming process one has to operate with the full belt width filled with insulation. If a narrower width is desired, then a full belt width must still be used in the single belt machine. A full width of insulation material coming out of the curing oven is longitudinally slit, but the full width is rolled up. After rolling, the surplus material can be removed from the rest of the roll. While the surplus material may be recycled as loose fill insulation or admix, this process is both an inconvenience and economically inefficient.
U.S. Pat. No. 6,321,507 addresses the telescoping issue by using at least two endless belts, partially overlapping in the loop forming area as well as the belt take-up area. With this design, the overall belt width can be adjusted by changing the degree to which the two belts overlap, to exactly match the product width needed. This is a complicated approach to the telescoping problem, and of course, does nothing to address other problems with the “free-loop” designs. These other problems include the following:    1. dealing with tremendous slack on the continuous belt when the rolled material is released (i.e. slack is the difference between the circular segment of belt encircling the roll, and the corresponding straight-line length of belt between the rollers, after the finished roll has been ejected). This slack often causes the belt to leave its guides; and    2. lack of control over the actual shape and quality of the roll. As the material typically takes on an irregular and inconsistent cross-section, handling and storage are difficult and inefficient. As well, the irregular shape will result in uneven compression which may damage the compressible material.
Another major class of roll-up machines employs a system of horizontal 150 and inclined belt 152 conveyors, and moveable forming rollers 154 to define a generally “triangular” roll forming space 156. An exemplary triangular cavity design is presented in FIG. 3.
An early design in this class of roll-up machines, based on a combined use of two belt conveyors and a forming or compression roller forming a triangular geometry is disclosed in U.S. Pat. No. 3,991,538. Further improvements are disclosed in U.S. Pat. Nos. 4,583,697; 4,608,807; 4,765,554; 4,928,898; 5,305,963; and 6,109,560 and in patents DE 296 04 901 U1; EP 0 941 952 A1 and EP 0 949 172 A1. These designs have various arrangements of driving and idle rollers, sensing devices (pressure and roll diameter, for example), position control devices and control algorithmsAll roll-up machines based on a triangular geometry offer, in principle, just a three-point contact between the product being rolled and the rigid, roll-shaping members over the whole roll circumference. Any compressive pressure that is applied, can only be exerted at three distinct contact points, or to be more precise, three contact zones or areas rather than points, since the material being handled is compressible and deforms under load. This does not change the basic fact, however, that the compressive force can only be applied to a limited area, instead of being distributed more or less uniformly over the whole roll circumference, as in the single-belt, “free-loop” roll-up machines. If one squeezes too much, in an attempt to end up with a tight roll with a high overall compression ratio, fibre breakage and/or binder bond loss is likely to occur in the compression zones, resulting in poor thickness recovery after unrolling.
As the roll diameter increases, so does the distance between the three pressure points along the roll circumference, and the travel time between subsequent pressure points. After leaving a given pressure point, the compressed material is no longer under pressure and will expand, at least to some degree, before reaching the next compression point, where it is compressed again. This cycle of compression and de-compression is repeated many times as the roll is formed, the repetitive loading damaging fibres and causing binder fatigue.
Triangular cavity roll-up machines are capable of forming rather loosely wound rolls of fibrous insulation material with an overall compression ratio of about 3.5:1, and therefore a second compression step is usually performed. This second compression step typically employs vacuum compression or mechanical pressure, and may result in a final compression ratio between 6:1 and 8:1. It is not that convenient or economical to have this two-stage operation; quite often the process is not fully automatic and requires additional manpower compared to one-step processes. This second-stage compression also causes further damage to the material because the material is in a fixed roll when the second compression is applied. It is therefore desirable to obtain similar compression ratios, in a single-stage operation.
The next group of roll-up machines of interest are those which employ rigid arcuate jaws. Two of such roll-up machines are described in U.S. Pat. Nos. 3,808,771 and 3,964,232. An exemplary schematic of such a design is presented in FIG. 4, employing two such arcuate jaws 160, 162. In both cases, open centre, loose rolls are formed, which yield about a 2:1 compression ratio.
The intention with the '771 and '232 designs is only to obtain a small degree of compression with the rolling stage (2:1), obtaining the balance of the desired compression in a second, vertical compression stage to obtain an overall compression of about 8:1. Limited compression can be obtained in the rolling stage because the arcuate jaws 160, 162 have a rigid shape and the shape of the cavity they define 164 does not stay circular as the roll grows.
After forming loose, oval-shaped rolls in the first stage, a number of rolls are stacked in a tall compression chamber, and are then compressed further by mechanical means.
This two-stage technique is slow, requires two machines, requires manual labour between the two stages, and damages the compressed material because of the tight compressed turns in the material, formed during the second stage.
Recently, “circular cavity” roll-up machines have begun to appear, which overcome various problems with the earlier designs, using two endless belts to define a generally circular roll-up cavity. An exemplary schematic diagram is presented in FIG. 5.
U.S. Pat. No. 5,425,512 for example, discloses two designs where separate endless belt systems 170, 172 are combined to form two arcuate belt lengths, almost entirely enveloping the roll of the compressible material 112 during the roll forming process.
The cavity 174 in which the winding of the compressed fibrous material takes place is defined by five rollers and two belt conveyors, one roller 176 being part of the bottom conveyor 178, and two downstream rollers 180, 182 which are not fixed in place, but moving away along rectilinear paths; their movement or travel being computer controlled. Two other rollers 184 and 186 are generally fixed in place. A variant of this circular cavity design in the '512 patent employs a complicated two carousel system to reduce the non-productive time between subsequent winding operations, the start of a new roll winding, taking place immediately after the ejection of an earlier roll of product. Each carousel has a set of three rollers mounted on 120-degree spaced arms, and only one roller at a time is used to make a given roll of product. A rather involved algorithm is required to control all the aspects of the roll winding and roll ejection process.
There are a number of major problems with two-belt roll-up machines in general. For example:    1. with a two-belt design it is quite difficult to start the formation of a new roll. If the two belts are held tight at the beginning of the process (which is necessary, to an extent, to compress the material being rolled), then the two belts do not define a cavity which aids in the rolling up of the material being compressed. Rather than having a circular or triangular cavity, the cavity is defined by two belts which are parallel to one another and travelling in opposite directions. Thus, the two-belt roll-up machine cannot start rolling the compressible material in a neat and uniform way. Typically, some extra mechanical means (apart from the two belts themselves), is employed to assist the starting of the roll.            One could start up the roll without any external means as shown in FIGS. 29A through 29C, but one would have to rely entirely on some taper added to the initial belt geometry in the roll forming zone, combined with the appropriate compressed mat thickness with respect to the entry gap height between the forming rollers of each belt segment. This concept could be used to start the roll satisfactorily but only at the expense of substantially enlarging the entry gap between the forming rollers.        Alternatively, FIGS. 30 through 33 present diagrams of a design where the process of the roll startup is mechanically aided by an external mechanical system.        Additional mechanical complication, extra cost, more maintenance, high dynamics of top belt configuration change and belt tracking are some of the issues which must be dealt with if one uses this design; while the two-belt designs have to deal with less slack than the “free loop” designs, the amount of slack on the continuous belts when the rolled material is released, is still a very significant problem. This slack can cause the belts to leave their guides during the operational cycle, so many designs used take up cylinders to absorb this slack. The more slack that has to be absorbed, the longer the travel of the take up cylinder system.        A more detailed discussion of slack is described hereinafter;            2. the two-belt designs known in the art also require a very quick and drastic change in the positions of the rollers for a speedy ejection of the roll of product; and    3. also similar to the “free loop” systems, two belt roll up machines do not maintain cross-section symmetry very well. This often results in geometrical distortion of the completed roll, commonly known as coning or telescoping.
There is therefore a need for a high-compression roll-up machine and method of rolling that results in consistent and uniformly shaped rolls, with minium damage to the material being rolled. This design must be mechanically straightforward and reliable, ideally using a simple control algorithm and control system.